Expression of protein kinase C isoforms in smooth muscle cells in various states of differentiation.

We analysed the expression of protein kinase C (PKC) isoforms in smooth muscle cells (SMC) in various states of differentiation, using Western blots and thermocycle amplification of mRNA. SMC isolated from intact tissues express three isoforms of PKC, namely alpha, delta, and zeta. Following cell culture, SMC additionally express mRNA for PKC-epsilon, but significant amounts of the corresponding protein were not detected. Transformed SMC, such as the cell line DDT1 MF-2, express both mRNA and protein for PKC-epsilon, lack the delta isoenzyme, whilst maintaining the expression of the alpha and zeta isoforms. Thus PKC-delta and epsilon isoenzyme expression appears to vary with the state of differentiation of these cells, with PKC-epsilon expression increasing as the cells become proliferative.